1. Field of the Invention
The present invention relates to truck coupling arrangements for releasably coupling the front end of a trailer to the rear end of a tractor for relative pivoting movement therebetween to facilitate turning of the truck.
2. History of the Prior Art
Various conventional arrangements are known for releasably coupling the front end of a trailer to the rear end of a tractor to provide pivoting movement therebetween so that the truck may turn. In one such conventional arrangement a downwardly extending pin at the underside of the front of the trailer is received and locked within an opening in a bearing plate at the rear end of the tractor. The bearing plate or "fifth wheel" which slopes somewhat downwardly at the rear end of the tractor is typically covered with grease or other lubricant to facilitate pivoting movement along the axis of the pin of the front of the trailer relative to the rear of the tractor during turning of the truck.
A common problem with articulated vehicles such as the conventional tractor and trailer arrangement just described lies in the tendency of the front of the trailer to move relatively quickly toward the inside of the turn as the truck begins a turning movement. This results in the driver of such truck having to "swing the truck wide" during many turns to avoid striking objects at the inside of the turn. Aside from being a source of considerable inconvenience, this problem is also a substantial safety hazard in areas such as city streets where the relatively late turning movement of the tractor required at many intersections and driveways may invite autos and other smaller vehicles to advance along the inside of the truck without realizing that the truck is turning. The problem is further complicated by the considerable effort and additional space that are required to back the truck into loading docks in areas of extremely limited space that were designed years ago to accommodate smaller trucks than those presently in existence.
Truck coupling arrangements have been proposed from the more traditional designs, as exemplified by U.S. Pat. No. 4,359,234 of Mittlestadt in which the coupling between a tractor and a trailer includes a pair of pin-like pivot members that ride within the curved track of a mating member. Other examples are provided by U.S. Pat. No. 2,680,627 of Johnson et al, U.S. Pat. No. 2,056,262 of Edwards, German Pat. No. 615,163 and German Pat. No. 617,125. However, these arrangements are directed to different problems such as the provision of close-coupling of the trailer to the tractor in the case of Mittlestadt and do not address the problem of delaying the inward movement of the front of the trailer during turning while at the same time maintaining other desirable characteristics such as proper distribution of the trailor load on the tractor.
Accordingly, it would be desirable to provide an improved truck coupling arrangement for the releasable and pivotable coupling of a trailer to a tractor.
It would further be desirable to provide an improved truck coupling arrangement which improves the tracking of the trailer by delaying the inward movement of the front of the trailer during turning so as to reduce the need for wide turning movement of the tractor during many turns made by the truck.